Step by step guide on how an automotive internal combustion engine works. This article information pertains to all vehicles except electric.

Step 1
- An internal combustion engine is designed to compress and combust a fuel air mixture which is controlled by the driver.

Automotive Internal Combustion Engine Cutaway

Step 2 - The engine begins by pulling air through the air intake throttle actuator which is controlled via the computer, and foot actuator that is located in the drivers compartment. This air flow is monitored by the mass air flow sensor and cleaned by the air filter.

Electronic Throttle Actuator

Step 3 - Once air has passed through the throttle actuator, it enters the intake manifold were it is divided among individual cylinder intake ports.

Intake Manifold

Step 4 - Air is then routed through the intake manifold were it enters individual intake ports contained within the cylinder head, which is controlled by a valve (intake.)

Intake Port Cutaway

Step 5 - Fuel enters the intake port or directly into the combustion chamber via a fuel injector which is controlled by the computer.

Port Fuel Injector

Step 6 - A camshaft is used to open each valve while it rotates as the engine is operating. A spring returns the valve to the closed position which is called a "valve spring". (Overhead camshaft configuration shown.)



Written by
Co-Founder and CEO of
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2015-01-07)